1. Field of the Invention
The present invention relates to a diesel engine system and a method of controlling a diesel engine.
2. Description of the Related Art
There is a general tendency today to employ an automatic stop/restart control system in a diesel engine. As described in Japanese Unexamined Patent Publication No. 2006-46251, for example, an automatic stop/restart control system of a diesel engine stops the engine when prescribed automatic engine stop conditions are satisfied and restarts the automatically stopped engine when prescribed engine restart conditions are satisfied.
For restarting the automatically stopped diesel engine, it is necessary to inject fuel into a cylinder which was in a compression stroke at automatic engine stop to induce self-ignition in the cylinder. A problem often encountered with a diesel engine having an automatic stop/restart feature is deterioration of starting performance which is caused by a reduction in engine temperature occurring after the automatic engine stop. The aforementioned Publication describes a conventional arrangement for supplying a large electric current to glow plugs of the diesel engine at the beginning of cranking as well as an approach to solving the problem by increasing the amount of electric current supplied to the glow plug of a cylinder which was in the compression stroke at engine stop compared to the amount of electric current supplied to the other glow plugs.
Although intended to improve ignitability (restartability) of the diesel engine, the aforementioned approach of the Publication will cause deterioration of fuel economy and more frequent replacement of the glow plugs. This is because the approach of the Publication aims at improving the ignitability by just increasing the amount of electric current supplied to the glow plug at engine restart, which necessitates an undue increase in the amount of electricity and energizing period of the glow plugs.